Thunderhead Explorer

I'm very proud to announce that we just released the 1.1 version of the Flex API For ArcGIS Server . Check it out, and tell us what you think. Happy mapping all.

Though sometimes an ArcGIS map service extends the full world, an application that uses this map service will want to restrict the extent to a way smaller extent. In this post, I will be talking about how to achieve this. Check out the application in action. Note that when you pan the map, it "springs" back to the initial extent. And even after you zoom in, the spring is still in effect. So how did I do this is as follows: I created a sub class of the Map class. In the constructor, I added a LOAD event listener. The LOAD event handler adds two EXTENT_CHANGE event listeners, where one of them is at a lower priority to guarantee that it will called last. This low priority listener sole purpose is to get and save the map extent as the initial extent. In addition, the initial scale is computed and saved too. Now, upon an extent change, we check if the initial extent intersects the new extent. if it does, then we compute the horizontal and vertical overlap distance and we ad...

In this post I'm demonstrating how to use Cocomo 's data messaging to enable collaborative mapping. One or more map application can share their active extent and whiteboard using the mouse. Though the application is not very sophisticated, it demonstrates the extensibility of the flex api and the power of Cocomo. BTW, I highly recommend that you read Ryan's blog post on how to get started with Cocomo. Using the CocomoDevConsole, I created a CollectionNode and named it 'cocomoMap', and I added two non-persistant Nodes . The application uses the node 'cocomoMapExtent' to publish and receive active map extents, and the node 'cocomoMapPoints' is used to publish and receive drawn polylines. One of the cool things that I like in Cocomo, is that you can register a class with the MessageItem registry to enable the publishing and receiving of message bodies in 'native' format. So, I registered the class SpatialReference , MapPoint , Polyline and...

I will be speaking at 360|Flex this year in Indianapolis. But this time, it was decided to let the community vote on subjects/speakers. So...I'm asking for your vote . The Title of the session is Yet Another Flex Mapping API - NOT! where we will demonstrate the Flex Mapping API For ArcGIS Server, where we will deconstruct live real-world mapping applications and algorithms such as dense clustering, auto labeling of features, collaborative editing, real-time asset tracking and client/server collaborative Geo-Processing. In addition, we will demonstrate how to create your own layer, geometry and symbol extensions for superior rendering performance taking advantage of the FP10 drawing API. Vote here and vote often.

In this post, I will be demonstrating how to label map points using the flex API for AGS. This work is strongly based on Kevin Mote’s “Fast Point-Feature Label Placement For Dynamic Visualization”. In this application, I’m loading city data from a shapefile. The city attributes contain the city name and rank. Rank is a number between 1 and 7 where 1 indicates a very populated city and 7 indicates a much lesser populated city. Upon a map load event, the shapefile is read and the cities with a rank less or equal to 3 are selected then sorted in descending rank order. Each shapefile record is converted into a LabelGraphic and added to a list. A LabelGraphic is a subclass of Graphic and has a TextField as a child. A ExtentChange event listener is added to the map, in such a way that whenever the map extent changes, a LabelManager is created to manage the LabelGraphics in the visible extent. A LabelManager has a spatial index (a trellis per Mote’s) to quickly locate label candidates (mo...

Following the last post, It would be nice to inspect the clustered set of map points when say the set is less than a dozen or so. In this post, I'm demonstrating something I call a FlareSymbol, which is a Symbol sub-class, where like before, the number of clustered points is shown. But, when you click on the cluster, it flares out to show the individual map points. Each flared point can react to say a mouse click to popup an info window showing its attribute values. When you click again on the cluster, it collapses the map points back to its center. Here it is in action. And like usual, you can download the source from here .

Was asked "what is the best way to display 20,000 markers on a map ?". Well, displaying all 20K map points does not make whole lot of sense, as you just see nothing, just a blanket of markers. A smarter approach is to cluster the points and display the clusters. Somebody pointed me to mapeed , and asked me to duplicate this using the Flex API for AGS. Here it is. I've loaded 20,000 map points from geonames and created dynamically clusters based on the scale of the map and its extent. BTW, this is all client side processing - gotta love the JIT in Flash Player :-) [Update] Sooo many people asked me for the source code of the app - here it is. Any feedback is more than welcome.